Seminar offers insights into avoiding Swimmer's Itch

Linda Gallagher, Contributing Writer

Shown is a diagram explaining the life cycle of the Swimmer's Itch parasite and how it can infect people enjoying the waters of northern Michigan. 


ALDEN – With the onset of summer weather and warmer waters, recreationists everywhere, including in both Antrim and Kalkaska counties, will be enjoying a refreshing swim in one of the area's beautiful freshwater lakes.

They'll also be suffering from Swimmer's Itch (aka Cercarial dermatitis), an irritating but harmless and temporary scourge that is believed to be an allergic reaction to an infection from a common waterborne parasite carried by waterfowl and other birds.

Ron Reimink, a nationally known expert on Swimmer's Itch, in conjunction with the Three Lakes Association, recently presented a seminar at the Helena Township Community Hall in Alden offering insights on the causes of the annual summer time malady, and tips on how to avoid it.

Along with other members of his team from Freshwater Solutions in Hudsonville – which works with lake associations across northern Michigan to reduce swimmer's itch, while striving to make breakthroughs in research – Reimink began the June 18 event by explaining the life cycle of the parasite causing Swimmer's Itch, and how it is contracted by swimmers and others enjoying the water. 

"Swimmer’s Itch probably has been around as long as humans," he said. "The condition was known to exist as early as the 1800s, but it was not until 1928 that a biologist found that the dermatitis was caused by the larval stage of a group of flatworm parasites in the family Schistosomatidae, which is carried by birds that frequent the water, primarily waterfowl such as ducks."

Not just mergansers, a species of fish-eating duck, carry the parasite as many believe, Reimink noted.

"Schistosome eggs have been found in many species of ducks, including mallards and wood ducks, as well as Canada geese, Mute swans, and some land birds that can be frequently found near water, such as Red-Winged blackbirds."

The eggs are released into the water through the birds' feces, which hatch and become a short-lived, non-feeding, free-living stage known as the miracidium.

Miracidium then seek out freshwater snails, where they then metamorphose into another free-living stage known as the cercaria. Cercaria will then emerge to float to the surface of the water and seek another host within a short 24-hour lifespan, which is usually waterfowl, where the life cycle will begin again, but, on occasion, people.

"Once it enters the skin, the cercaria will die immediately, but in people can cause an inflammatory immune reaction before doing so that we know as Swimmer's Itch," said Reimink.

"This reaction causes initially mildly itchy spots on the skin, but within 24-48 hours the spots become raised papules which are intensely itchy," he said. "Each papule corresponds to the penetration site of a single parasite."

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